The Power-Transition Crisis of the 160s–130s BCE and the Formation of the Parthian Empire

I IR Theory and the Rise of Parthia

Although the Parthian state certainly was quite different than modern nation-states, around which International Relations theory developed, it was a nuanced and highly effective imperial power that rivalled the abilities and accomplishments of any ancient state. The growth and development of the Parthian state, which scholars usually discuss in the traditional terms of political history – good leadership, the inclusiveness of Parthian rule, Parthian adaptability, or the declining strength of Parthia’s neighbors – is better understood with International Relations theory, specifically the theoretical framework of Realism.^[14] Realism emphasizes the unforgiving and competitive nature of interactions between states within an international system of states that lacks enforceable international law and/or central authority, known as interstate anarchy.^[15] This article employs Realist Theory (specifically a Neorealist or “structural” approach to international relations, which is the study of how system structures affect international behaviors and outcomes) as a framework to help provide greater perspective and a more expansive understanding of state decision-making and interaction in the ancient world.^[16] In this endeavor I share Eckstein’s preference for the use of the sub-school of Realist theory called “offensive” Realism when analyzing ancient international environments because of the comparatively primitive and violent characteristics of these environments in the ancient world.^[17] Offensive Realism maintains that states seek to maximize their security and power through domination and hegemony because of the anarchic nature of many interstate systems (or international communities in which states interact and compete).^[18] Systems of militarized interstate anarchy were common in the ancient world, including the systems that developed in the Hellenistic Middle East.

In the 240s-230s, Seleucid control of their eastern lands declined suddenly as a series of costly wars against Ptolemaic Egypt and dynastic disputes sapped Seleucid strength. In particular the sudden death of Antiochus II (in 246), the Seleucid defeat in the Third Syrian War (246–241), and the subsequent civil war for the throne (ca. 240–236) severely damaged the reputation and military might of the Seleucid Empire.^[19] This unexpected decline of Seleucid power in the 240 s caused what international relations theorists call a “power-transition crisis” (or a sudden and dramatic fluctuation of a state’s power within an interstate system) in the Hellenistic Middle East.^[20] Although a power-transition crisis does not in and of itself cause war, it makes hegemonic war, which is a large-scale war that reorders or creates a new interstate structure that better reflects the realities of power distribution and balance of power within the system, more likely because it destabilizes the interstate system and brings power relations into question.^[21] This is precisely what happened in the 240s–230s as Parthia and Bactria emerged as rival powers to the Seleucid Empire on the Iranian plateau.^[22]

With the emergence of rival states within the Hellenistic Middle East in the middle third century, the international environment once dominated by the Seleucid Empire suddenly and drastically changed.^[23] Parthia in northeastern Iran and Bactria in Afghanistan challenged Seleucid hegemony on the Iranian plateau, and the major interstate system, which had incorporated all the Greek lands of the eastern Mediterranean and the Persian-held regions of the Middle East since the Persian Wars, abruptly and effectively split.^[24] What International Relations theorists call an interstate system of “tripolarity” (or the rivalry of three dominant states) between Antigonid Macedon, Ptolemaic Egypt, and the Seleucid powerbase in Syria remained in place in the west in the new, more focused “Eastern Mediterranean interstate system.”^[25] Yet a turbulent and rather ambiguous tripolarity between Parthia, Bactria, and the Seleucid Empire also emerged in the east in what we may call the newly formed “Iranian interstate system.”^[26]

After the emergence of the Iranian interstate system by the 230 s, Parthia and Bactria no longer concerned themselves directly with the geopolitical developments and rivalries of the eastern Mediterranean, which remained the focus of the traditional Hellenistic Successor states until the rise of Roman unipolar hegemony over the entire Mediterranean from the 190s–160s.^[27] Moreover, the geopolitical developments of the Iranian interstate system were only intermittently and indirectly related to those of the eastern Mediterranean interstate system through sporadic Seleucid efforts to reclaim their lost eastern lands in the 230 s, 200 s, 180 s, 160 s, 130 s, and 120 s.

Thus, the Seleucid Empire came to operate simultaneously in separate major interstate systems, which is a geopolitical distinction shared by several other large, powerful empires throughout history.^[28] A good illustration of this separation between the geopolitical developments in the west and those in the east is the fact that all of our surviving sources view events in Syria and Babylonia as separate from one another in this period.^[29] The geopolitical developments in the east, especially those concerning Parthia, had no direct connection to the emerging international environment of the Graeco-Roman Mediterranean world. They instead belonged to a separate interstate system in the east that was only indirectly affected by western developments.

The major difference between the participation of the Seleucids in the eastern Mediterranean interstate system and the Iranian interstate system was the political, cultural, and economic focus of the Seleucids. The Seleucids controlled one of the largest empires in the world in this period, establishing themselves as the imperial successors of Alexander and the Persians in the Middle East; however, they appear to have had a slightly different outlook on their hegemony in the east than their predecessors. Alexander and the Persians had viewed their imperial space as limitless on the central Asia steppe and in the Indian subcontinent; however, Kosmin recently has argued that the Seleucids formed stricter limitations on their imperial space, especially along their eastern frontier, with “explicit and formal recognition of equal peer kingdoms.”^[30] Although, at least in theory, it is unlikely that the Seleucid kings abandoned their royal ideology of unlimited, universal rule, practical concerns in the west encouraged the Seleucids to develop a more restricted policy in the east.^[31] Therefore, Kosmin’s arguments for the limitation of Seleucid hegemony in the east, where the Seleucids actually restricted and shrank the limits of their imperialism when they created an “ideological limes” along the frontier of the central Asian steppe and in 306/305 ceded the Indus River valley and Arachosia (modern southern Pakistan) to the Mauryan Emperor, Chandragupta, in exchange for 500 war elephants, generally appear sound.^[32] The Seleucids decided to establish Bactria (modern northern Afghanistan) as a bulwark to protect the eastern edge of their empire and turned their attention to the geopolitical developments of the eastern Mediterranean.^[33]

Since the Seleucids came to favor western geopolitical developments and rivalries, their participation in the eastern Mediterranean interstate system was active, aggressive, and frequent. Meanwhile, their participation in the Iranian interstate system was reactive, inconsistent, and sporadic.^[34] Although the Seleucid state remained an important power in the east, possessing the potential strength to threaten the survival of Parthia and Bactria, the Parthians and Bactrians continually took advantage of the Seleucids’ western distractions to maximize their regional security and power, adding to their own regional rivalry.

The newly formed Iranian interstate system paralleled those found in the Mediterranean. It was a harsh international environment with multiple militarized, bellicose, and aggressive polities. There was no enforceable international law, a lack of ameliorative diplomacy, and no way to understand the realities of power relations between states short of open conflict.^[35] The Parthians faced serious threats to their security and survival from Hellenistic kings, native Iranian dynasties, and central Asian tribes. The crisis of the 240s-230s weakened the Seleucid state and distracted the Seleucid kings, fracturing the eastern frontier; however, the potential power of the Seleucid state remained considerable. There would be six attempted campaigns to reconquer the lands of the east over the course of a century by five different Seleucid kings: Seleucus II, Antiochus III, Antiochus IV, Demetrius II, and Antiochus VII. This clearly demonstrates the strength of their resolve to contest the Parthians and reclaim their lost territories. Yet only one of those campaigns was successful. This chaotic and dangerous international environment helped influence the Parthians’ policies as they struggled, first, to survive within the Iranian interstate system and, later, to expand and dominate that system.

The Parthians maintained their kingdom through bloodshed and compromise in the late third and early second centuries, just trying to survive in a dangerous and unforgiving environment where massacre, mass enslavement, or even total destruction were continual concerns.^[36] Yet by the middle second century an opportunity arose to maximize their security and power as another major crisis gripped the Hellenistic Middle East. Within a generation the international environment once again suddenly and drastically changed. The Parthians emerged as the true rival of the Seleucids, dominating many of the lands once held by the successors of Alexander and significantly altering the course of history in the east.

II The Crisis Begins

By the 230 s, Arsaces I, the first king of the Parthians, had forged a strong independent state in northeastern Iran, and when the Seleucid king, Seleucus II, invaded to reclaim these lost lands, the Parthians defeated him, strengthening their position and safeguarding the existence of the Parthian kingdom.^[37] The task of reestablishing Seleucid hegemony over the Iranian plateau next fell to Seleucus’ son, Antiochus III, who conducted a grand campaign (210–205), reoccupying large sections of eastern Iran, western Afghanistan, and southern Pakistan and establishing Parthia, Bactria, and an Indian kingdom in the northern Indus River valley as subordinate allies (Polyb. 10.28.5–31.1–13, 11.34.9–12; Just. Epit. 41.5.7). Unfortunately for the Seleucids, although Antiochus’ eastern campaign had forced the kings of Parthia and Bactria to become his subordinate allies, the volatility of his new network of subordinate allied kingdoms presented subsequent Seleucid kings with a major challenge. Once Antiochus or one of his subordinate allies died, the previous arrangement had to be renewed diplomatically or by force.^[38] Few of Antiochus’ successors shared his diplomatic influence or military capability, and the resilience and proficiency of the Parthians played a fundamental role in undermining the sustainability of Antiochus’ model of loose imperialism over subordinate allied kingdoms in the east in the second century.^[39] Since the competence of the Seleucid king in many ways dictated the ability of the state to maintain its hegemony, without a strong and determined central leader, the Seleucid Empire faltered, especially in the east. Once new leaders emerged in Parthia and Bactria, there was little incentive to submit willingly to the Seleucids, and therefore, a new eastern campaign was necessary about once a generation to maintain or reestablish Seleucid hegemony in the east.^[40]

Moreover, Antiochus III’s defeat in his war against Rome (192–188) once again drastically reshaped the international environment. The Seleucids came to function within three distinct major interstate systems: The Roman-dominated Mediterranean interstate system, the Seleucid-dominated Iranian interstate system, and the emerging multipolar Near Eastern interstate system that stretched from Egypt to eastern Anatolia over to the Caucasus and Mesopotamia. This new Near Eastern interstate system featured the rivalry of the Seleucids and Ptolemies but also included the actions of numerous middling and minor states, including the Hasmonean Kingdom in Judaea, Cappadocia in southeastern Anatolia, Pontus in northeastern Anatolia, Armenia, and various Arab tribes.

Although in the 180s-170s the Seleucid Empire remained the leading power in the Iranian interstate system, numerous distractions in the west and a series of military and political setbacks provided the Parthians with many opportunities to regain and expand their former strength.^[41] By the 160 s, the Seleucids to the west of Parthia and the Bactrians to the east of Parthia faced mounting difficulties that helped create another power-transition crisis in the Hellenistic Middle East, and the Parthians, especially under the leadership of Mithridates I, once again emerged as the great beneficiaries of this crisis. It is clear the Seleucids recognized the importance of reinforcing their wavering hegemony throughout the Iranian plateau. In fact, Antiochus III died in 187 while preparing for a second eastern campaign.^[42] Then in early 165, Antiochus’ youngest son, Antiochus IV, began his own abortive eastern expedition.^[43]

Although Antiochus IV was in the middle of suppressing the Maccabean Revolt in Judaea, the Parthians’ sudden and violent invasion of Hyrcania (modern northern Iran) in early 165 diverted Antiochus’ attention.^[44] The fifth book of Maccabees (7.10–13) records,

And it was told to king Antiochus [IV] what Mattathias and his son Judas had done. News of this came also to the king of the Persians [that is, the king of the Parthians]; so that he [likely Phraates I] played false with Antiochus, departing from his friendship, following the example of Judas. Which giving Antiochus a great deal of uneasiness, he called to him one of his household officers named Lysias, a stout and brave man, and said to him, “I have now determined to go into the land of Persia [that is, Parthia] to make war; and I wish to leave behind me my son [Antiochus V] in my stead; and to take with me half of my army, and to leave the remainder with my son.”^[45]

Meanwhile, Tacitus (Hist. 5.8) states, “King Antiochus [IV] endeavored to abolish Jewish superstition and to introduce Greek civilization; the war with the Parthians, however, prevented his improving this basest of peoples; for it was exactly at that time that Arsaces had revolted [desciverat].” These accounts illustrate that Antiochus left Judaea hastily to pursue a war against the Parthians in the east late in his reign. However, the exact context of Antiochus’ eastern campaign is debated, and some scholars reject Tacitus’ comment as an error because of his use of the name “Arsaces.” Scholars, beginning with Moore, have accused Tacitus, first, of not knowing that Arsaces I seized Parthia in the middle of the third century and, second, of confusing the actions of Arsaces I here with the Maccabean Revolt.^[46] Yet there is good reason to reject such criticisms. Nothing about Tacitus’ comment definitively connects this “Arsaces” to Arsaces I. In fact, the Romans knew that all Parthian kings regardless of their original name took the name Arsaces upon their ascension as a royal title, much like the Romans used the titles Caesar and Augustus.^[47] It is far more likely that Tacitus here simply refers to the reigning Parthian king by his regal name, Arsaces, and therefore, we must consider, first, who was the Parthian king in 165 and, second, what this man had done to gain the full attention of Antiochus IV (Just. Epit. 41.5.1–6; Strabo 15.1.36).

The traditional date for the accession of Mithridates I to the Parthian throne is ca. 171, which would mean Antiochus IV conducted his eastern campaign to challenge Mithridates’ rising ambitions in the east; however, evidence that Mithridates became king in 171 is inconclusive. Instead, Assar recently has made a convincing argument to shift the beginning of Mithridates’ reign forward to ca. 165/164 and to alter Phraates I’s reign to ca. 168–165/164.^[48] Therefore, Mithridates’ older brother, Phraates, could have been king when Antiochus began his eastern campaign. In fact, the passages from V Maccabees and Tacitus provide further evidence for this new chronology. In V Maccabees the Parthian king betrayed Antiochus’ “friendship,” and Tacitus claims the Parthians had “revolted.” These depictions make far more sense if we associate them with Phraates instead of Mithridates.^[49]

The passage in V Maccabees perhaps illustrates that, following the death of Antiochus III, Parthian kings, such as Arsaces II, Phriapatius, Arsaces IV, and Phraates I had renewed terms of friendship with Seleucus IV and Antiochus IV.^[50] Yet it is clear that the Parthians first acted aggressively against the interests of the Seleucids after a long period of peace when Phraates I attacked the Mardians and began to reoccupy Hyrcania in early 165 (Just. Epit. 41.5.9). With the attack against Hyrcania taking place while the Seleucids were occupied in Judaea, Phraates’ actions were perhaps even a deliberate exploitation of the Seleucids’ overtaxed logistical load.

The sudden western expansion of Phraates I was a blatant violation of the status quo between the Parthians and Seleucids established by Antiochus III.^[51] Thus, Phraates drastically altered the relationship of the Parthians and Seleucids, not Mithridates I, finally casting off friendly relations and violently rebelling against Seleucid hegemony. The sudden belligerence and success of Phraates concerned Antiochus IV and demanded a rapid Seleucid response. With half of the Seleucid military, Antiochus undertook a major retaliatory campaign aimed to punish the Parthians and restore Seleucid hegemony over the east.^[52]

Before Phraates I died in ca. 165/164 he named his younger brother, Mithridates I, his successor. To do this Phraates set aside several of his adult sons (Just. Epit. 41.5.9–10). It is possible that Phraates, fearing his rapidly declining health, left the kingdom in his brother’s more capable hands to secure the positive momentum of the dynasty and state.^[53] Certainly, Mithridates shared his brother’s emphasis on aggressive foreign policy, and Phraates’ decision proved critical as Mithridates built off the momentum of his brother to raise the Parthian state to new heights of power.^[54]

In terms of International Relations theory, under the long reign of Mithridates I (ca. 165/164–132) the Parthian state began its transition from a limited revisionist state, looking primarily to maximize its security regionally, to an unlimited revisionist state, looking to replace the current makeup of the Iranian interstate system with its own hegemony.^[55] The Parthians became no longer satisfied with regional power and influence on the Iranian plateau, instead becoming increasingly determined to supplant the Seleucids as the leading power in the Hellenistic Middle East.^[56] Mithridates’ aggressive and capable leadership was at the center of this transition.

Antiochus III’s anabasis (210–205) had devastated the Parthian kingdom. The aggression of the Seleucid state, the failures of the Parthian military, and the drastic reversal of Parthian fortunes at the end of the third century served as a warning to the Parthians about the potential threat of neighbors and the need to maximize state power.^[57] Justin states that the Parthians came to seek vengeance against Seleucid aggression (Epit. 42.1.1). Mithridates I looked not only to recover the lost lands of Arsaces I’s kingdom, but also to establish Parthia as the leading power in the Iranian interstate system. This was a momentous period of Parthian history that demands further attention and consideration.^[58] Opportunity, motivation, and capability all aligned for the Parthians as Mithridates settled old scores against the Seleucid Empire through hegemonic war. Mithridates was a daring and gifted military leader, and like his brother, he wasted little time in capitalizing on the renewed strength of the Parthian military, completing the reconquest of Hyrcania.^[59]

In 165 Antiochus IV recognized the renewed aggression of the Parthians as a serious threat and closely followed the example of his father, Antiochus III, in preparing his eastern campaign. First, he organized his large army, placed trusted officials in charge of his western lands, and protected the position of his young son, Antiochus V (App. Syr. 8.45; V Macc. 7.10–13; cf. I Macc. 3.27–37). Second, he secured his northern frontier by subduing Armenia (Diod. Sic. 31.17a; App. Syr. 8.45, 11.66; Porph. 38, 55–56). Finally, he sought out a great sum of money to support his eastern expedition.

In 187 Antiochus III had attempted to loot a temple in southwestern Iran to finance another eastern expedition; however, he died in the attempt.^[60] In need of money to finance his own major eastern expedition and perhaps motivated by a desire to avenge the violent death of his father, Antiochus IV also chose to attempt to plunder a temple in southwestern Iran (Polyb. 31.9; Joseph. AJ 12.354–9; App. Syr. 11.66; II Macc. 9.1–3; Porph. 56). His assault faced similar stiff resistance and ended in abysmal failure. Antiochus did not die in the attack like his father; however, his failure in southwestern Iran derailed his eastern expedition. He lacked the money and no longer had the men to attack the Parthians immediately. Although the cause is much debated in the sources, Antiochus suddenly died, likely from disease, near Gabae (modern Isfahan, Iran) in late 164 while trying to salvage his eastern campaign.^[61]

With the sudden death of Antiochus IV in the east, the Seleucid throne passed to his nine-year-old son, Antiochus V, whose short reign (164–161) was dominated by conflict, political intrigue, and Roman influence (App. Syr. 8.46–47; Joseph. AJ 12.360–361). The boy’s regent, Lysias, had far too many concerns in the west to follow up on Antiochus IV’s plans to subdue the Parthians. Thus, the burgeoning Parthian state avoided a major invasion that likely would have severely jeopardized its newly reacquired independence, and this respite from Seleucid retaliation allowed Mithridates I to pursue his aggressive foreign policy and military operations throughout the Iranian plateau. The collapse of the Seleucid government after the unexpected death of Antiochus IV exactly fits the theory of “power-transition crisis,” where one pillar of the interstate system suddenly weakens (while another expands in power).

Much like the power-transition crisis of the 240s-230s that followed the setbacks of Antiochus II’s reign, the power-transition crisis of the 160s-130s provided the Parthians with an immense opportunity to expand their strength and standing drastically at the direct expense of the damaged and distracted Seleucid Empire.^[62] Moreover, much like the rebellions of the Seleucid governors Andragoras in Parthia and Diodotus in Bactria during the power-transition crisis of the 240s–230s, the power-transition crisis of the 160s–130s afforded satraps in Media (northwestern Iran), Elymais (southwestern Iran), Persis (southern Iran), and Characene (southern Mesopotamia) the opportunity to rebel. As the Seleucid Empire once again began to fragment, Mithridates I and his regime established Parthia as the undisputed power on the Iranian plateau and the leading rival of the Seleucids within the expanding Iranian interstate system.

III The crisis continues

After becoming king in 175, Antiochus IV appointed his close friend Timarchus to the major command of viceroy over the Upper Satrapies (App. Syr. 8.45; Diod. Sic. 31.27a). While Antiochus fought the Ptolemies and Jews in the west, Timarchus was the chief official in charge of maintaining the strength and influence of the Seleucids in the east. From his headquarters in Media, Timarchus witnessed the sudden aggression of Phraates I as he attacked the Mardians and began to reoccupy Hyrcania. In fact, it is likely that Timarchus was the official who sent urgent word to Antiochus in Judaea, stressing the seriousness of the Parthian threat (V Macc. 7.10–13). As one of Antiochus’ closest friends and most powerful advisers, Timarchus’ warning would have carried considerable weight and helps explain Antiochus’ swift response to the deteriorating situation in the east. Although Antiochus likely marched his army from Judaea through Syria, Armenia, Babylonia, Elymais and finally to Persis in southern Iran before his sudden death, he also appears to have included Media in his plans for attacking the Parthians and likely had been in communication with Timarchus during the campaign.^[63] Yet Antiochus’ sudden death in 164 swiftly ended his plans of eastern conquest, left the Parthians unmolested, and isolated Timarchus.

With Antiochus IV dead, the boy king Antiochus V was not capable of maintaining his position or managing the kingdom. His father’s advisors, Lysias, Philip, Timarchus, and Heracleides, and Antiochus V’s twenty-two-year-old cousin Demetrius all vied for power and influence within the wavering empire. Much like Andragoras and Diodotus before him, without a strong central authority to help protect the eastern lands of the empire and with mounting pressures threatening the security of his lands, Timarchus soon decided to declare independence in Media. Another series of civil wars threatened to fracture the Seleucid state.

In terms of International Relations theory, the sudden aggression of Parthia and the turmoil that followed the death of Antiochus IV caused another power-transition crisis in the Hellenistic Middle East. This crisis, which lasted from the late 160 s to the early 130 s, facilitated extensive Parthian conquests, expanding the bounds of the Iranian interstate system and causing it to overlap with the lands of the Near Eastern interstate system for the first time. By the late 160 s, the rapidly shifting geopolitical situation in the Hellenistic Middle East had helped foster a dangerous international environment of heightened uncertainty and anxiety between polities.^[64] For example, Justin (Epit. 41.6.1–3, 6–7) emphasizes the uncertainty of power relations between Parthia and Bactria in this period and the violence of the international environment, stressing the sudden and unexpected decline of Bactria under the pressures of “various wars” and the rise of Parthia “to the highest degree of power.”

The sudden resurgence of the Parthians in the Iranian interstate system drastically altered power relations. Widespread conflict and rapid change facilitated and perpetuated the power-transition crisis of the 160s-130s as the hegemony of the Seleucids fractured temporarily into a multipolar system of numerous competing polities.^[65] The systemic pressures of the interstate anarchy within the Iranian interstate system (for example, heightened militarism, uncertain power capabilities, lack of security, fear of destruction) encouraged aggression and open conflict between numerous states and statesmen during the crisis to eliminate potential threats and to establish a new, more reliable distribution of power throughout the Hellenistic Middle East.^[66] The hostile and unstable international environment of the Hellenistic Middle East during the power-transition crisis of the 160s-130s helped encourage the aggressive foreign policies of several leaders, including Mithridates I in Parthia and Timarchus in Media.

This chaotic environment provided Mithridates I with a great opportunity to implement aggressive foreign policy and expand his kingdom at the expense of the Parthians’ rivals. The important frontier region of Bactria became Mithridates’ first target. Continual dynastic conflicts and an ongoing rivalry with the Indo-Greek Kingdom in northern India increasingly distracted the Bactrian kings and sapped the strength of their kingdom, gradually drawing the Bactrians’ attention away from their precarious northern and western borders.^[67] During the crisis Bactria became increasingly vulnerable to nomadic and Parthian aggression in this chaotic environment.

Mithridates I conducted a successful war against Bactria by the middle 150 s (and perhaps as early as 163/162).^[68] The Parthians conquered the western portions of Aria (western Afghanistan) and Margiana (eastern Turkmenistan) in this conflict, significantly expanding their eastern territory and raising their profile within the Hellenistic Middle East.^[69] Mithridates even implemented new imperial imagery on his coinage to signify his victory over the Bactrian Greeks.^[70] His victory drastically shifted the power balance on the Iranian plateau in Parthia’s favor, and Bactria never again emerged as a major actor in the geopolitics of this region.

Meanwhile, Timarchus, who had spent over a decade in Media consolidating his power and wealth, found himself in a vulnerable position with the sudden death of Antiochus IV. Timarchus had no ability to influence Antiochus’ young son, Antiochus V, who was under the control of the royal advisor Lysias in Syria. When Antiochus V’s cousin, Demetrius I, escaped from his captivity at Rome, executed Antiochus V and Lysias, and seized the Seleucid throne in 162/161, Timarchus was unable to intervene and unwilling to accept this usurper, declaring himself king in Media soon afterward.^[71] Timarchus quickly raised “an army of considerable size” and forged a military alliance against Demetrius with King Artaxias of Armenia, who had taken advantage of the crisis to reassert his independence (Diod. Sic. 31.27a).

Timarchus utilized his large army and new alliance to rapidly expand his territory outside of Media. Diodorus (31.27a) states, “Having, moreover, intimidated the neighboring peoples by an impressive display of force, and brought many of them under his sway, he marched against Zeugma [on the Euphrates], and eventually gained control of the kingdom.” Although Diodorus exaggerates Timarchus’ success in the war against Demetrius I, Timarchus began to call himself “Great King” and possibly gained control of Media Atropatene and Elymais before occupying Babylonia in 161/160.^[72]

Scholars continue to debate the actions of the Parthians during the Seleucid civil war. The crisis eventually encouraged the Parthians to invade Media; however, it is unclear if Mithridates I attacked Media before Timarchus marched west to fight Demetrius I. Recently, Olbrycht argued that Timarchus probably repulsed Parthian attacks in the late 160 s, which allowed him to secure his eastern frontier before invading Babylonia.^[73] Meanwhile, Grainger suggests that Timarchus and Mithridates made an agreement that limited Parthian expansion westward.^[74] Finally, Taylor claims that Timarchus “scored a major victory over the Parthians and used this victory to proclaim himself king.”^[75] Yet there simply is no evidence that directly links Timarchus to a conflict or a treaty with the Parthians.

To connect Timarchus to the Parthians, scholars have cited a passage from Justin (Epit. 41.6.6–7), which states, “During the course of these proceedings among the Bactrians [that is, the Indian wars of Eucratides I], a war arose between the Parthians and Medes, and after fortune on each side had been some time fluctuating, victory at length fell to the Parthians. Mithridates [I], enforced with this addition to his power, appointed Bagasis over Media, while he himself marched into Hyrcania.”^[76] Justin here illustrates that there was a long struggle for Media; however, Justin plainly states that this conflict did not occur until Eucratides had invaded India, which most likely occurred after Mithridates’ successful war against the Bactrians in the late 160 s or early 150 s.^[77] Moreover, after invading Babylonia in 161, Timarchus’ reign was short. Demetrius I occupied Babylonia and Media soon after his defeat of Timarchus in 160.^[78] Therefore, the available window for a conflict between Timarchus and the Parthians is extremely small.

The evidence does not support Taylor’s assertion that Timarchus decisively defeated the Parthians and used that victory to declare himself king. In fact, Diodorus (31.27a). demonstrates clearly that Timarchus declared himself king in direct opposition to the usurpation of Demetrius I. Meanwhile, Grainger’s conclusion that Timarchus would not have been able to rebel in Media if the Parthians had been free to attack him ignores that Androgoras and Diodotus had done exactly that in the face of the aggression of the Parni under Arsaces I in the 240 s.^[79] Instead, the collapse of Seleucid authority after Antiochus IV’s death and the growing power of Mithridates I were the exact reasons for Timarchus’ rebellion. Moreover, there also is little reason to accept Grainger’s suggestion that Timarchus and Mithridates forged a treaty.

Timarchus had been the strong ally of Antiochus IV, who had threatened to conquer and punish the Parthians in 164. Yet Demetrius I’s usurpation of Antiochus V’s throne, encouraged Timarchus to declare his kingship and necessitated a civil war. Timarchus was hostile toward the Parthians; however, he could not afford to attack Parthia in 162/161 before dealing with Demetrius in the west. Meanwhile, Mithridates I had little reason to befriend the hostile Timarchus nor, more importantly, to limit his own western military ambitions willingly (Just. Epit. 41.6.6–9). A favorable treaty between Timarchus and Mithridates was plausible only after a decisive engagement, for which no evidence exists.

Despite the assumptions of recent scholars, it seems highly unlikely that Timarchus clashed with the Parthians in the late 160 s. If Timarchus declared himself king in 162/161, he would have needed time to organize his army, forge his alliance with Armenia, and consolidate his power over his immediate neighbors before invading Babylonia in 161/160. Meanwhile, Mithridates I was not ignorant of the considerable power Timarchus wielded in Media even after the death of Antiochus IV. Timarchus had spent over a decade strengthening the defenses of Media, and his diligent efforts of course help explain why it later took the Parthians so long to subdue the region. Diodorus (31.27a) records that Timarchus was one of the most powerful men in the Hellenistic Middle East in the late 160 s, and he used this strong position to frighten and coerce his regional rivals. In fact, the Parthians likely were one of the neighboring peoples whom Timarchus intimidated with his impressive display of force early in his reign.

In the late 160 s the Parthians remained a minor power just beginning to reemerge from decades of recovery.^[80] After consolidating the recent territorial gains of his brother, Mithridates I readied for the defense of Hyrcania and Parthia in 165/164.^[81] The failure of Antiochus IV’s eastern campaign saved Parthia from invasion; however, Timarchus’ position in Media remained strong. Mithridates simply did not have the resources in 163/162 to invade Media, and the unraveling crisis within the Seleucid Empire encouraged Timarchus to remain cautious in Media.^[82]

Timarchus and Mithridates I found themselves in a stalemate. Neither leader could hope to overwhelm the other without first securing more resources, so they turned their attentions to other targets. Timarchus became involved in the Seleucid civil war in the west, and Mithridates quickly turned his attention to the vulnerable frontier of Bactria. By the time Mithridates completed his war against Eucratides I and occupied large sections of Aria and Margiana, he did not have time to organize and conduct major operations against Media before Timarchus’ occupation of Babylonia in 161 and his death in 160. Thus, the long and difficult campaign of Mithridates to conquer Media most likely did not occur until the 150 s.

IV The Parthian conquest of Media

Even though Timarchus and Mithridates I did not go to war in the late 160 s, large-scale conflict between the Parthians and Seleucids became increasingly likely as the Hellenistic Middle East descended into the power-transition crisis of the 160s–130s. Conflict had already emerged in Media, Babylonia, Aria, and Margiana, and rebellions in Elymais and Persis destabilized the region further.^[83] The eastern lands of the Seleucid Empire became increasingly vulnerable to the rising power of the Parthians, and the renewed aggression of the Parthians on the Iranian plateau demanded Seleucid retaliation. It was in this period that a new phase of hegemonic warfare between the Parthians and Seleucids began to determine the new balance of power in the Iranian interstate system as the Parthians gradually strove to replace Seleucid hegemony and dominate the Hellenistic Middle East.^[84]

By the end of the 160 s, the Parthians controlled Parthia, Hyrcania, Aria, and Margiana, adding significantly to their logistical and financial capabilities. With new resources and a stronger eastern frontier, Mithridates I was in a better position to challenge the Seleucids in the west. Western expansion into Media, Persia, and Mesopotamia offered major political and financial incentives for the Parthians; however, the conquest and occupation of these regions proved immensely difficult as the Seleucids and regional dynasts challenged Parthia’s rising hegemony frequently.

With the defeat of Timarchus in 160, Demetrius I regained control of Babylonia and Media, restoring the integrity of the empire at least temporarily. Demetrius’ success in this civil war led Grainger to suggest recently that Mithridates I waited ten years to attack Media after Timarchus’ defeat because “the Seleukid state under Demetrios I was strong enough to deter any adventure by the Parthian King.”^[85] However, this stance is too dismissive of the evidence and exaggerates Demetrius’ position in the 150 s. Although Demetrius was able to overcome Timarchus, his control over the empire was fragile and western concerns dominated his attention.

Demetrius I had poor relations with the Romans after his escape from captivity, which his success in seizing power in Syria did not alleviate (App. Syr. 8.45–47; Polyb. 31.11–15; I Macc. 7.1). In 160 Demetrius placed generals in charge of the defense of his eastern satrapies and immediately returned to the west, where he sent considerable gifts to the Romans to appease their anger.^[86] Yet the gifts did little to satisfy the Romans, and when Demetrius attempted to intervene in Cappadocia (southeastern Anatolia) in 159, the Romans quickly overruled his decision.^[87] Justin (Epit. 35.1.1) states, “Demetrius, having possessed himself of the throne of Syria, and thinking that peace might be dangerous in the unsettled state of his affairs, resolved to enlarge the borders of his kingdom, and increase his power, by making war upon his neighbors.” Justin illustrates that Demetrius recognized his vulnerable position, and it is not surprising that he chose to act aggressively to expand his security and power against a weak neighboring state. Yet Demetrius was unable to invade Cappadocia or to install a puppet ruler because of the severe limitations of his power and influence within the Roman-dominated Mediterranean interstate system.^[88] The Romans’ decision to protect Cappadocia was meant to reassert their hegemony at the direct expense of Demetrius’ regime, and the situation in Cappadocia was an embarrassment for Demetrius that called into question his strength and legitimacy, severely limiting his effectiveness in the 150 s.

After the fiasco in Cappadocia, the capital city of Antioch rebelled against Demetrius’ rule, eventually leading to Alexander Balas openly challenging Demetrius for the Seleucid throne in 152.^[89] Despite the weak claim to the throne of Alexander, Demetrius continued to mismanage his affairs, and Alexander eventually gained the support of the Jews and Ptolemaic Egypt in the civil war (I Macc. 10.1, 21, 46–47, 51–58; App. Syr. 11.67). Demetrius was unable to repeat his success against Timarchus and died in battle against Alexander in 150 (Just. Epit. 35.1.9–2.2; I Macc. 10.48–50; Joseph. AJ 13.116–119).

Thus, Demetrius I spent his entire tumultuous reign (162–150) suppressing revolts, fighting rivals to his throne, and trying to reconsolidate the power of the empire. He had every reason and desire to act aggressively against neighboring states, which included Parthia; however, he lacked the capability to do so. Justin tells us that Mithridates I’s conquest of Media was a long affair with multiple setbacks, and Moses of Chorene indicates that Mithridates fought the generals of Demetrius in Media during this struggle.^[90] Demetrius was never strong enough to “deter” the Parthians from attacking Media. In fact, his ineffectiveness and vulnerability encouraged the Parthians to attack his isolated generals in the east.

Grainger’s recent conclusions, first, that Mithridates I did not attack Media until after Alexander Balas became king in 150 to avoid Demetrius I’s power, second, that Mithridates justified his attack against Alexander because he was a Seleucid usurper, and, third, that Mithridates hoped to revive Achaemenid legitimacy under the Arsacid dynasty are not tenable.^[91] There simply is no convincing evidence to support such conclusions. Demetrius’ regime was vulnerable, the Arsacids were not yet concerned with the dynastic politics of the Seleucids, and the Parthians’ interest in an Achaemenid revival for their imperial propaganda arguably did not develop until their much later conflict with imperial Rome.^[92] Instead, Mithridates began his campaign to conquer Media and Media Atropatene as early as 158 and no later than 155.^[93] Mithridates did not need to justify his aggression against the Seleucids in Media along strong ideological or propagandistic lines; rather, he had far more compelling practical concerns, such as the expansion of his power against a vulnerable rival.

Although the western affairs of the empire during the crisis demanded Demetrius I’s attention, the Parthians found the conquest of Media slow and difficult because of a determined resistance by various Seleucid generals made possible in part by the prior efforts of Timarchus to establish the region as a military stronghold. Mithridates I likely subjugated Media Atropatene as a tributary kingdom in the north; however, the strong defensive positions of the Seleucids in the south and their successful counterattacks turned the campaign into a war of attrition.^[94] An unfinished Greek-Aramaic inscription on a carving of Heracles Triumphant at the Bisitun Pass in what is western Iran today, dated 148, gives us a good indication of the back and forth Seleucid and Parthian contest during the long conquest of Media.^[95] The inscription asks for the safety of Cleomenes, the Seleucid viceroy of the Upper Satrapies in Media at the time.^[96] The association of the inscription with Heracles Triumphant perhaps indicates that Cleomenes had won a victory against the Parthians as late as 148, signifying one of the many reversals of the Parthians’ fortunes during this conflict mentioned by Justin.^[97] The inscription also illustrates that the Seleucids still occupied parts of Media in 148 and that the permanent Parthian conquest of the region was not complete until after this date.^[98] Mithridates marked his final annexation of Media by making his brother the new satrap of the region in ca. 147 and by issuing a series of commemorative coins.^[99]

V The crisis expands

The continued aggression of the Parthians and an ongoing series of Seleucid civil wars perpetuated the power-transition crisis of the 160s-130s in the Hellenistic Middle East. Although Alexander Balas killed Demetrius I in battle in 150, his rule similarly was vulnerable and dominated by western concerns (Just. Epit. 35.1.9–2.2; I Macc. 10.48–50; Joseph. AJ 13.116–119.). Alexander had been a usurper of questionable lineage, and his efforts to gain legitimacy through a marriage alliance with Ptolemaic Egypt ultimately failed (I Macc. 10.51–8; Diod. Sic. 32.9c). Further, his generals in the east, although they continued to frustrate Mithridates I’s advances in Media, were unable to eliminate the threat of the Parthians to the eastern lands of the empire.^[100] In 147, as Media finally fell to the Parthians, Demetrius’ eldest son, Demetrius II, arrived in Syria with the support of Ptolemy VI to contest Alexander’s throne, and the Seleucid Empire again descended into civil war.^[101]

In 145, Demetrius II and Ptolemy VI defeated Alexander Balas decisively in battle and secured his assassination.^[102] Yet although Demetrius won the war, Media was lost, and he had to hand over control of Coele Syria to Ptolemaic Egypt in exchange for Ptolemy’s military support and a marriage to his daughter, Cleopatra Thea. Further, dynastic strife, ineffective administration, and poor military leadership plagued Demetrius’ regime.^[103] Demetrius quickly found that the growing factionalism of the Seleucid state presented him with numerous potential rivals and several unhappy communities. Widespread unrest in Syria encouraged the general Diodotus Tryphon to make a bid for power as the guardian of Alexander’s young son, Antiochus VI, and the Seleucid Empire descended into an even longer, more difficult civil war from 145–138.^[104]

The power, prestige, and influence of the Seleucids was in jeopardy, and to make matters worse, Rome, Ptolemaic Egypt, and Parthia were not the only concerns of the Seleucids during the crisis. In the 160 s, Elymais and Persis in southern Iran appear to have followed the examples of Parthia, Bactria, and Media, asserting their local autonomy and briefly breaking away from the Seleucid Empire.^[105] Then in the 140 s the mounting troubles of the Seleucid state allowed Elymais and Persis to assert their independence once again.^[106] Meanwhile, Characene, which controlled the Euphrates and Tigris delta, also actively began asserting its autonomy in this period (ca. 141).^[107] Moreover, the vulnerability of the Seleucid state encouraged Arab raids to begin penetrating the southern frontier.^[108]

Yet the Parthians had emerged suddenly as the most pressing threat to the survival of the Seleucid state. The decline of Seleucid hegemony and the rapid rise of conflict throughout the Hellenistic Middle East during the crisis created a power vacuum that the Parthians eagerly began to fill. Mithridates I’s conquest of Media, although difficult, and his control over the passes of the Zagros Mountains were crucial to further Parthian expansion to the west and south. Moreover, control of Media also gave the Parthians direct access to the important breeding grounds of the famous Nisaean horses of the Medes.^[109] The Parthian military increasingly required large numbers of quality horses and, although there is no evidence to suggest that the Parthians targeted this region strictly to gain access to this resource, control of these breeding grounds would have strengthened their army.^[110] Media quickly became a center of Parthian power and wealth, and as the crisis continued to unfold, Mithridates began to target the wealthy, urbanized, and vulnerable lands of Mesopotamia in the late 140 s.^[111]

VI The Parthians’ difficult western frontier

Unfortunately, our sources for this period of Mithridates I’s reign are vague and often at odds in the reconstruction of events. Justin (Epit. 41.6.7–8) records that Mithridates returned to Hyrcania after finalizing his conquest of Media, later returning to the west to conquer Elymais and then Mesopotamia. Yet a fragment of the Babylonian Astronomical Diaries states that Mithridates conquered Babylonia by the summer of 141 and then returned to Hyrcania, before marching to conquer Elymais.^[112]

The difficult Parthian conquest and occupation of Media was complete by the end of 147; however, consolidating Parthian control over the region took several more years to accomplish. While Mithridates I and his brother, Bagasis, began the challenging work of strengthening Parthia’s new western frontier, Mithridates had to monitor developments in the east closely (Just. Epit. 41.6.6–7). Mithridates likely returned to the east in 145 in response to two new threats. First, the Bactrian king Eucratides I died in 145 at the hands of his son.^[113] Therefore, Mithridates needed to return east to make sure that the new king of Bactria (there were three possible competing candidates: Heliocles I, Eucratides II, and Platon) had no intentions to act aggressively toward him.^[114] Second, and more importantly, the kingdom of Bactria was beginning to crumble under the mounting pressures of the invasions of the nomadic Saka and Yuezhi.^[115] In particular the wealthy and prosperous northern city Ai Khanoum likely fell to these invaders in ca. 146/145.^[116] Bactria had always been a key bulwark against the tribal confederations of this region; however, as the Bactrians sapped their strength with dynastic conflicts and wars in India, and as the violent displacement of the Yuezhi initiated a widespread migratory period for both them and the Saka toward Sogdiana (modern southern Kazakhstan, eastern Uzbekistan, Kyrgyzstan, and Tajikistan), the Bactrians increasingly were unable to defend their northern and eastern frontiers.^[117] With Eucratides I dead and his kingdom rapidly deteriorating, Mithridates could not ignore the growing vulnerability of Parthia’s eastern frontier. Since becoming king in 165/164, Mithridates had quadrupled the size of the Parthian state and had made Parthia the leading power on the Iranian plateau; however, the Parthians’ hegemony in the east remained vulnerable. From 147–141 Mithridates worked diligently to consolidate and secure the expanded frontiers of the Parthian state, also perhaps subduing tribes in southeastern Iran and southwestern Pakistan while he was in the east.^[118]

Mithridates I’s continued efforts to strengthen and protect his eastern frontier were successful, at least temporarily; however, the wealthy lands of Mesopotamia, Elymais, and Persis remained tempting targets along the Parthians’ extensive western frontier. In 141 Mithridates decided to risk the stability of his eastern frontier to strike at the heart of the Seleucid Empire. Late that spring he invaded and occupied Babylonia, which the Seleucids had mostly abandoned during the ongoing civil war between Demetrius II and Diodotus Tryphon in Syria, and Mithridates entered the symbolically powerful cities of Seleucia and Babylon as a triumphant conqueror, appointing governors of Macedonian descent to maximize support in the region.^[119]

It is also likely that Persis fell under Parthian control at this time.^[120] Mithridates I’s strategy could have been to organize his forces in Media, perhaps near Ecbatana, and then to strike rapidly in a two-pronged expedition. He clearly led the main Parthian force to conquer Babylonia; however, a trusted general, perhaps Bagasis, seemingly subdued Persis. These conquests expanded the bounds of the Iranian interstate system further west across the vast lands of Mesopotamia, which had been a part of the separate Near Eastern interstate system since the 180 s, creating for the first time what international relations theorist call “system overlap” between the separate Iranian and Near Eastern interstate systems.^[121] Although the Seleucids continued to contest Parthian hegemony in Mesopotamia for decades, these lands were now firmly established within the bounds of the expanding Iranian interstate system, and they were another significant step in the rapid growth of Parthia as an unlimited revisionist state within that interstate system.

The campaign in 141 was Mithridates I’s most aggressive and direct challenge to the deteriorating hegemony of the Seleucid Empire in the Hellenistic Middle East. The Parthians’ control of the royal capital of Seleucus I was a glaring representation of their new position of power. In fact, control of Media, Persis, and Babylonia made Parthia far more than just a regional power, and the occupation of Babylonia’s great cities in particular provided the Parthians with great prestige and immense wealth.^[122] Mithridates immediately struck a new series of silver tetradrachms (S13.1–2) in Seleucia on the Tigris, in which he adopted the epithet “Admirer of the Greeks,” to commemorate his victory and appease the large Greek and Macedonian population in the area.^[123]

With their conquests of Babylonia and Persis, which had been the administrative centers of the Achaemenids, Alexander the Great, and Seleucus I, the Parthians for the first time could claim to be the hegemonic rivals of the Seleucids. Moreover, the power-transition crisis of the 160s–130s had provided Mithridates with an immense opportunity to transform Parthia from a minor kingdom into an imperial power. The success of the Parthians and the threat they posed to the Seleucids assured further conflict between the two powers. The Seleucids could not let the aggression of the Parthians and, in particular, the loss of Babylonia, go unanswered, and the Parthians, who continued to expand westward for another half-century, had no intentions to limit their western ambitions to this region as the rising hegemon in the Iranian interstate system and as a newly formed unlimited revisionist state.^[124]

Although further major conflict between the two leading powers of the Hellenistic Middle East was on the horizon, the Seleucids and Parthians had several other concerns threatening their security in this period. After the occupation of Babylonia in 141, the Babylonian Astronomical Diaries record that Mithridates I again abruptly returned to the east.^[125] Mithridates’ immediate return to the Iranian plateau helps illustrate that, first, the conquests of Babylonia and Persis in 141 had been aggressive and opportunistic and, second, the eastern frontier continued to be in jeopardy. Assar, utilizing a passage from Strabo, even suggests that Mithridates returned to the east at this time to counter steppe invaders.^[126] Although we have no definitive evidence of military encounters between the Parthians and the Saka at this time, Mithridates understood the considerable threat of the encroaching nomadic warriors and believed that his eastern lands were vulnerable.^[127]

Mithridates I’s decision to return to the east also illustrates that he did not anticipate the immediate challenges the Parthians faced to their occupation of Babylonia. The Babylonian Astronomical Diaries record that almost immediately following his departure from the region the recently independent people of Elymais from southwestern Iran invaded and began ravaging the territory, forcing Mithridates to return.^[128] The Elymaeans even burned Apamea on the Tigris before Mithridates and his generals counterattacked toward their capital, Susa.^[129]

The power-transition crisis of the 160s–130s threw Mesopotamia into chaos with the region changing hands on no less than eleven occasions in this period (Timarchus in 161–160, Demetrius I in 160, Alexander Balas ca. 150, Demetrius II ca. 145, the Parthians in 141, the Elymaeans in 141/140, the Parthians in 140; Demetrius II in 139/138, the Parthians in 138, the Elymaeans in 138/137, and the Parthians in 137).^[130] Rebellions, raids, and a series of invasions destabilized and devastated the region, creating opportunity and incentive for further violence. The Parthians recognized the troubled state of Babylonia and the surrounding territories, conducting aggressive conquests.^[131]

Even though his chronology of events is confused, Justin records that Mithridates I defeated the Elymaeans and conquered Elymais.^[132] Yet the Parthians’ conquest of Elymais also was quite complicated. While the Parthians attempted to counter the advances of the Elymaeans, it is possible that the Seleucid usurper, Diodotus Tryphon, tried unsuccessfully to reestablish Seleucid control over Babylonia in 140.^[133] Moreover, although Mithridates seized Susa and issued a series of bronze coins (S12.26–28) from its mint in 140–138, Shayegan recently has demonstrated that Elymais and Parthia had an ongoing conflict over Mesopotamia and Susiana until the Parthians finally forced Elymais to recognize Parthian suzerainty in 132 and accept Parthian direct rule in 124.^[134]

For several years prior to the conflict with Parthia, Elymais had acted independently of the Seleucid Empire. In 147 in reaction to the destructive civil war between Demetrius II and Alexander Balas, the rulers of Elymais had declared themselves kings and began raiding Babylonia for the next fifteen years.^[135] Thus, Elymais was one of many states within the expanding Iranian interstate system taking advantage of the decline of Seleucid hegemony during the power-transition crisis of the 160s-130s, pursuing power-maximizing policies to increase state security and authority. Much like Bactria, Parthia, and Media before them, Elymais and the other middling and minor states in the Hellenistic Middle East, such as Media Atropatene, Persis, Characene, and Armenia, chafed under Seleucid suzerainty in the first half of the second century. These states desired to rule themselves autonomously; however, until the sudden deterioration of Seleucid power, beginning in the late 160 s and continuing into the 130 s, they did not have the capabilities to resist Seleucid retaliation.^[136]

The temporary independence of these middling and minor states during the crisis and their aggressive efforts to secure their own power and safety further destabilized the international environment. In an unforgiving system of interstate anarchy like the Iranian interstate system in the 160s-130s, where violence and brutality were constant threats, minor states needed to be highly militarized and bellicose to survive.^[137] Thus, it is not surprising that smaller powers, such as the Hasmonean Kingdom, Commagene, Cappadocia, Armenia, Elymais, Characene, Persis, Media Atropatene, Bactria, the Indo-Greek Kingdom, various Arab and central Asian tribes, and especially Parthia all emphasized aggressive militarism against neighboring powers in this period of crisis.^[138] The fracturing of Seleucid hegemony in the middle second century meant that the Seleucids and Parthians not only had to reckon with one another, but also had to contend with several highly militarized, expansionistic middling and minor states in this period.

VII The Results of the Crisis

It was in this uncertain, fluid, and dangerous international environment that the Seleucids determined to retaliate in the hegemonic struggle against Parthia. Although recent civil wars, rebellions, and territorial losses to the Parthians had severely damaged the authority of the Seleucid kings and the perceived power of the empire, the Seleucid state remained a major military power in the Hellenistic Middle East with massive resources.^[139] Demetrius II and his successor, Antiochus VII, decided to undertake major eastern campaigns to punish the Parthians, to salvage the deteriorating prestige of the Seleucid state, and to restore the empire to its former glory.^[140] The Parthians had annexed Media, Persis, and Babylonia; however, each of these recent successes had been difficult and none of them had come at the expense of the main Seleucid royal army. The Parthians’ conquest of Media against limited Seleucid forces had taken years to accomplish, and the recent Elymaean raids into Babylonia illustrated the fragility of the Parthian occupation of this region. The newly acquired power of Parthia in the east remained quite fragile in 140. A determined, well-executed eastern campaign like that of Antiochus III in 210 could have reversed the recent gains of the Parthians swiftly and reestablished Seleucid hegemony over the Iranian interstate system, at least temporarily.

In 138 and 130 Demetrius II and then Antiochus VII had the opportunity, resources, and motivation to conduct major eastern expeditions against the Parthians. Yet both campaigns proved disastrous as they and their armies became isolated and fell victim to the Parthians’ mobile and deceptive mode of warfare.^[141] With these decisive victories, the Parthians established themselves firmly as the hegemonic rivals and geopolitical equals of the Seleucids within the Hellenistic Middle East. Antiochus VII’s eastern campaign was the last great gasp of the Seleucid Empire, and the Parthians’ victory provided them with an opening to push their advantage into the lands of the Near East for the first time.

Ultimately, Parthia under the leadership of Mithridates I emerged from the crisis as the most successful of numerous competing polities for three main reasons. First, the Parthians’ relatively moderate and inclusive style of governing aided them in their efforts to absorb huge swaths of territory throughout the Iranian plateau and Mesopotamia.^[142] The Parthians embraced regional aristocracies and incorporate them into a more flexible structure of empire.^[143] The Parthian state from its conception built upon the social flexibility of a multi-cultural union of regional leaders under the ultimate authority of the Arsacids.^[144] This made the high command of the Parthian state versatile and eclectic, allowing the Arsacids to develop a more inclusive system of administration that emphasized, utilized, and internalized the capabilities and strengths of local leaders.^[145] Although the Achaemenids utilized administrative inclusiveness and cultural flexibility to gain and maintain support within their massive empire, the Seleucids failed to persuade sufficiently “indigenous elites to identify imperial interest with their own.”^[146] The more dismissive and exploitative occupation of the multi-cultural eastern territories by the Seleucids, which in the examples of Seleucus II, Antiochus III, Antiochus IV, and Antiochus VII resulted in disaster, created local resentment on a scale that the Parthians rarely encountered.^[147] Thus, compared to the Seleucid occupation of the Middle East, indigenous aristocrats had heightened regional autonomy and power under the Parthians with greater access to authority and participation within the Parthian imperial system.^[148]

Second, the composition of the Parthian military, its use in the field, and its ability to maintain a major imperial state allowed the Parthians to dominate the Hellenistic Middle East. The Parthians utilized a mixture of swift, light-armed horse archers and perhaps the most devastating and versatile heavy cavalry in the world in this period to outmaneuver and overwhelm their competitors.^[149] Since the Parthians’ professional standing army was relatively small, they utilized their network of vassal kingdoms to raise necessary levies and share the military burden of controlling such a large imperial territory.^[150] The Parthians’ developed a highly effective approach to warfare that allowed smaller, more logistically limited, and lighter-armed Parthian armies to resist and annihilate the more professionalized and heavier-armed armies of the Seleucids and Romans through speed, maneuverability, flexibility, and deception.^[151]

Finally, the generally good leadership and relative stability of the Arsacids went hand-in-hand with the success of the Parthian state in this period. Unlike the Seleucids and Bactrians, who became crippled by dynastic strife during the crisis, the Arsacids did not experience a civil war until the late 90 s BCE.^[152] The stability of the monarchy during their early history gave the Parthians another important advantage in their struggle to dominate the Hellenistic Middle East. When the Parthian king was a capable and commanding figure, like Mithridates I, the state prospered; however, when the king was weak, or the throne was contested, something that occurred far too frequently after the late 90 s, the power of the state dwindled. The expanding power of the Parthian aristocracy played an important role in the long cycle of civil wars that sapped the strength of the Arsacids from the first century onward.^[153] Yet the capable and ambitious early Arsacids were indispensable to the formation and expansion of the Parthian state from a minor kingdom to a major empire.

Thus, Mithridates I’s leadership indeed was crucial to the success of the Parthian state in the 160s–130s, and his many conquests established him as one of the greatest kings of Parthia.^[154] Yet the environment in which he operated also is an important factor to consider. Without the power-transition crisis of the 160s–130s caused by the rapid collapse of Bactria and the death of Antiochus IV, the success Mithridates achieved would have been far more difficult and perhaps impossible. The death of Antiochus saved Parthia from a major invasion; the numerous distractions hamstringing Eucratides I’s regime in Bactria made easy eastern expansion possible; and the debilitating civil wars in Syria exposed Media and Mesopotamia to conquest. Understanding the circumstances of Mithridates’ reign is critical to appreciating his true accomplishments. He was not a unique leader in his desires to consolidate and expand his power; however, his capabilities were significant, and his opportunities were immense.

In the 160s–130s, Mithridates I was well-placed at the head of an ascending power during a period of widespread crisis to capitalize on the greatest opportunity the Parthians had had to greatly expand their power and influence since the 240s–230s. The crisis drastically changed the makeup of the international environment and created a power vacuum throughout much of the Hellenistic Middle East that the Parthians eagerly and expertly filled. Justin (Epit. 41.1.6–9) in the introduction of his Parthian history states,

It must seem wonderful to everyone, that they [the Parthians] should have reached such a height of good fortune as to rule over those nations under whose sway they had been merely slaves. Being assailed by the Romans, also, in three wars, under the conduct of the greatest generals, and at the most flourishing period of the republic, they alone, of all nations, were not only a match for them, but came off victorious; though it may have been a greater glory to them, indeed, to have been able to rise amidst the Assyrian, Median, and Persian empires, so celebrated of old, and the most powerful dominion of Bactria, peopled with a thousand cities, than to have been victorious in war against a people [the Romans] that came from a distance; especially when they were continually harassed by severe wars with the Scythians and other neighboring nations, and pressed with various other formidable contests.

Justin here labels the Parthians as the successors and equals of the greatest eastern empires, and he champions the significance of the Parthians’ rise to power, stressing the continued success of the Parthians in their numerous military confrontations. Although the rivalry with the Seleucids continued for another half century and soon after the rivalry with the Romans lasted another three centuries, the Parthians meteoric rise in the second century earned them a place in history as one of the world’s greatest powers.^[155]